(a) Any improvement or unit of work when the cost, according
to the estimate of the engineer, will exceed six thousand five
hundred dollars ($6,500), shall be done by contract and shall be let
to the lowest responsible bidder or bidders in the manner provided in
this article. The board shall first determine whether the contract
shall be let as a single unit, or shall be divided into severable
parts, or both, according to the best interests of the district. The
board shall call for bids and advertise the call by three insertions
in a daily newspaper of general circulation or by two insertions in a
weekly newspaper of general circulation printed in the district
inviting sealed proposals for the construction or performance of the
improvement or work before any contract is made. The call for bids
shall state whether the work is to be performed as a unit or shall be
divided into severable parts, or both, as stated in the call. The
board may let the work by single contract or it may divide the work
into severable parts by separate contracts, as stated in the call,
according to the best interests of the district. The board shall
require the successful bidder or bidders to file with the board a
good and sufficient bond, to be approved by the board, conditioned
upon the payment of their claims for labor and material. The bond
shall contain the terms and conditions set forth in Title 3
(commencing with Section 9000) of Part 6 of Division 4 of the Civil
Code and be subject to the provisions of that title. The board may
reject any and all bids and readvertise for new bids, or by a
two-thirds vote may elect to undertake the work by force account.
(b) If no proposals are received pursuant to advertisement or the
estimated cost of the work does not exceed six thousand five hundred
dollars ($6,500), or the work consists of channel protection,
maintenance work, or emergency work, the board of supervisors may,
without advertising for bids, have the work done by employees of the
district, by day labor, under the direction of the board, by
contract, or by a combination of those methods. In case of an
emergency, if notice for bids to let contracts will not be given, the
board shall comply with Chapter 2.5 (commencing with Section 22050).
(c) The district may acquire in the open market, without
advertising for bids, materials, equipment, and supplies for use in
any work or for any other purpose; provided, however, that materials
and supplies for use in any new construction work or improvement,
except that work referred to in subdivision (b), may not be purchased
if the cost exceeds six thousand five hundred dollars ($6,500),
without advertising for bids and awarding the contract to the lowest
responsible bidder.